ML032760444

Technical Specifications Pages, Amendments 217 & 199

ML032760444
Person / Time
Site:	McGuire, Mcguire
Issue date:	09/29/2003
From:	NRC/NRR/DLPM
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Ice Bed 3.6.12 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.6.12.2 --------- NOTE----- I The chemical analysis may be performed on either the liquid solution or on the resulting ice.

Verify, by chemical analysis, that ice added to the ice Each ice addition condenser meets the boron concentration and pH requirements of SR 3.6.12.7.

SR 3.6.12.3 Verify by visual inspection, accumulation of ice on 18 months I structural members comprising flow channels through the ice bed is < 15 percent blockage of the total flow area for each safety analysis section.

SR 3.6.12.4 Verify total mass of stored ice is 2 1,890,000 lbs by 18 months calculating the mass of stored ice, at a 95 percent confidence, in each of three Radial Zones as defined below, by selecting a random sample of 2 30 ice baskets in each Radial Zone, and Verify:

to

1. Zone A (radial rows 8, 9), has a total mass of

> 313,200 lbs

2. Zone B (radial rows 4, 5, 6, 7), has a total mass of

> 901,000 bs

3. Zone C (radial rows 1, 2, 3), has a total mass of

> 675,800 lbs SR 3.6.12.5 Verify that the ice mass of each basket sampled in SR 18 months 3.6.12.4 is 2 600 lbs.

(continued)

McGuire Units 1 and 2 3.6.12-2 Amendment Nos. 217/199

Ice Bed 3.6.12 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.6.12.6 Visually inspect, for detrimental structural wear, cracks, 40 months corrosion, or other damage, two ice baskets from each group of bays as defined below:

a. Group 1 - bays 1 through 8;

b. Group 2 - bays 9 through 16; and

c. Group 3 - bays 17 through 24.

SR 3.6.12.7 ----------------- --------

The requirements of this SR are satisfied if the boron concentration and pH values obtained from averaging the individual sample results are within the limits specified below.

Verify, by chemical analysis of the stored ice in at least 54 months one randomly selected ice basket from each ice condenser bay, that ice bed:

a. Boron concentration is > 1800 ppm and < 2330 ppm; and

b. pH is 9.0 and < 9.5.

McGuire Units 1 and 2 3.6.12-3 Amendment Nos. 217/199

Ice Bed B 3.6.12 B 3.6 CONTAINMENT SYSTEMS B 3.6.12 Ice Bed BASES BACKGROUND The ice bed consists of a minimum of 1,890,000 lbs of ice stored within the ice condenser. The primary purpose of the ice bed is to provide a large heat sink in the event of a release of energy from a Design Basis Accident (DBA) in containment. The ice would absorb energy and limit containment peak pressure and temperature during the accident transient. Limiting the pressure and temperature reduces the release of fission product radioactivity from containment to the environment in the event of a DBA.

The ice condenser is an annular compartment enclosing approximately 3000 of the perimeter of the upper containment compartment, but penetrating the operating deck so that a portion extends Into the lower containment compartment. The lower portion has a series of hinged doors exposed to the atmosphere of the lower containment compartment, which, for normal unit operation, are designed to remain closed. At the top of the ice condenser is another set of doors exposed to the atmosphere of the upper compartment, which also remain closed during normal unit operation. Intermediate deck doors, located below the top deck doors, form the floor of a plenum at the upper part of the ice condenser. These doors also remain closed during normal unit operation.

The upper plenum area Is used to facilitate surveillance and maintenance of the ce bed.

The ice baskets contain the ice within the ice condenser. The ice bed is considered to consist of the total volume from the bottom elevation of the ice baskets to the top elevation of the ice baskets. The ice baskets position the ice within the ice bed in an arrangement to promote heat transfer from steam to ice. This arrangement enhances the ice condenser's primary function of condensing steam and absorbing heat energy released to the containment during a DBA.

In the event of a DBA, the ice condenser inlet doors (located below the operating deck) open due to the pressure rise in the lower compartment.

This allows air and steam to flow from the lower compartment into the ice condenser. The resulting pressure increase within the ice condenser causes the intermediate deck doors and the top deck doors to open, which allows the air to flow out of the ice condenser into the upper compartment. Steam condensation within the ice condenser limits the pressure and temperature buildup in containment. A divider barrier (i.e.,

operating deck and extensions thereof) separates the upper and lower compartments and ensures that the steam is directed into the ice condenser.

McGuire Unit 1 and 2 B 3.6.12-1 Revision No. 47

Ice Bed B 3.6.12 BASES BACKGROUND (continued)

The ice, together with the containment spray, Is adequate to absorb the initial blowdown of steam and water from a DBA and the additional heat loads that would enter containment during several hours following the initial blowdown. The additional heat loads would come from the residual heat in the reactor core, the hot piping and components, and the secondary system, including the steam generators. During the post blowdown period, the Air Return System (ARS) returns upper compartment air through the divider barrier to the lower compartment.

This serves to equalize pressures in containment and to continue circulating heated air and steam from the lower compartment through the ice condenser where the heat is removed by the remaining ice.

As ice melts, the water passes through the ice condenser floor drains Into the lower compartment. Thus, a second function of the ice bed is to be a large source of borated water (via the containment sump) for long term Emergency Core Cooling System (ECCS) and Containment Spray System heat removal functions in the recirculation mode.

A third function of the Ice bed and melted ice is to remove fission product iodine that may be released from the core during a DBA. Iodine removal occurs during the ice melt phase of the accident and continues as the melted ice is sprayed into the containment atmosphere by the Containment Spray System. The ice is adjusted to an alkaline pH that facilitates removal of radioactive iodine from the containment atmosphere.

The alkaline pH also minimizes the occurrence of the chloride and caustic stress corrosion on mechanical systems and components exposed to ECCS and Containment Spray System fluids In the recirculation mode of operation.

It is important for ice to exist In the ice baskets, the ice to be appropriately distributed around the 24 ice condenser bays, and for open flow paths to exist around ice baskets. This is especially important during the initial blowdown so that the steam and water mixture entering the lower compartment do not pass through only part of the Ice condenser, depleting the Ice there while bypassing the ice in other bays.

Two phenomena that can degrade the ice bed during the long service period are:

a. Loss of ice by melting or sublimation; and

b. Obstruction of flow passages through the ice bed due to buildup of Ice.

Both of these degrading phenomena are reduced by minimizing air leakage into and out of the ice condenser.

McGuire Units 1 and 2 B 3.6.12-2 Revision No. 47

Ice Bed B 3.6.12 BASES BACKGROUND (continued)

The ice bed limits the temperature and pressure that could be expected following a DBA, thus limiting leakage of fission product radioactivity from containment to the environment.

APPLICABLE The limiting DBAs considered relative to containment temperature and SAFETY ANALYSES pressure are the loss of coolant accident (LOCA) and the steam line break (SLB). The LOCA and SLB are analyzed using computer codes designed to predict the resultant containment pressure and temperature transients. DBAs are not assumed to occur simultaneously or consecutively.

Although the ice condenser is a passive system that requires no electrical power to perform its function, the Containment Spray System, RHR Spray System, and the ARS also function to assist the ice bed in limiting pressures and temperatures. Therefore, the postulated DBAs are analyzed In regards to containment Engineered Safety Feature (ESF) systems, assuming the loss of one ESF bus, which Is the worst case single active failure and results in one train each of the Containment Spray System, RHR Spray System, and ARS being Inoperable.

The limiting DBA analyses (Ref. 1) show that the maximum peak containment pressure results from the LOCA analysis and is calculated to be less than the containment design pressure. For certain aspects of the transient accident analyses, maximizing the calculated containment pressure is not conservative. In particular, the cooling effectiveness of the ECCS during the core reflood phase of a LOCA analysis Increases with Increasing containment backpressure. For these calculations, the containment backpressure Is calculated in a manner designed to conservatively minimize, rather than maximize, the calculated transient containment pressures, in accordance with 10 CFR 50, Appendix K (Ref. 2).

The maximum peak containment atmosphere temperature results from the SLB analysis and is discussed in the Bases for LCO 3.6.5, "Containment Air Temperature."

In addition to calculating the overall peak containment pressures, the DBA analyses include calculation of the transient differential pressures that occur across subcompartment walls during the initial blowdown phase of the accident transient. The internal containment walls and structures are designed to withstand these local transient pressure differentials for the limiting DBAs.

The ice bed satisfies Criterion 3 of 10 CFR 50.36 (Ref. 3).

McGuire Units 1 and 2 B 3.6.12-3 Revision No. 47

Ice Bed B 3.6.12 BASES LCO The ice bed LCO requires the existence of the required quantity of stored ice, appropriate distribution of the ice and the ice bed, open flow paths through the ce bed, and appropriate chemical content and pH of the stored ice. The stored ice functions to absorb heat during the blowdown phase and long term phase of a DBA, thereby limiting containment air temperature and pressure. The chemical content and pH of the stored ice provide core SDM (boron content) and remove radioactive iodine from the containment atmosphere when the melted ice is recirculated through the ECCS and the Containment Spray System, respectively.

APPLICABILITY In MODES 1, 2, 3, and 4, a DBA could cause an increase In containment pressure and temperature requiring the operation of the Ice bed.

Therefore, the LCO Is applicable in MODES 1, 2, 3, and 4.

In MODES 5 and 6, the probability and consequences of these events are reduced due to the pressure and temperature limitations of these MODES. Therefore, the ice bed is not required to be OPERABLE in these MODES.

ACTIONS A.1 If the ice bed is inoperable, It must be restored to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The Completion Time was developed based on operating experience, which confirms that due to the very large mass of stored ice, the parameters comprising OPERABILITY do not change appreciably in this time period. Because of this fact, the Surveillance Frequencies are long (months), except for the Ice bed temperature, which is checked every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. If a degraded condition is Identified, even for temperature, with such a large mass of ice it is not possible for the degraded condition to significantly degrade further In a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> period.

Therefore, 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is a reasonable amount of time to correct a degraded condition before initiating a shutdown.

B.1 and B.2 If the ice bed cannot be restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.

McGuire Units 1 and 2 B 3.6.12-4 Revision No. 47

Ice Bed B 3.6.12 BASES SURVEILLANCE SR 3.6.12.1 REQUIREMENTS Verifying that the maximum temperature of the ice bed is < 271F ensures that the ice is kept well below the melting point. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Frequency was based on operating experience, which confirmed that, due to the large mass of stored Ice, it is not possible for the ice bed temperature to degrade significantly within a 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> period and was also based on assessing the proximity of the LCO limit to the melting temperature.

Furthermore, the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> Frequency is considered adequate in view of Indications in the control room, including the alarm, to alert the operator to an abnormal ice bed temperature condition. This SR may be satisfied by use of the Ice Bed Temperature Monitoring System.

SR 3.6.12.2 This SR ensures that initial ce fill and any subsequent ice additions meet the boron concentration and pH requirements of SR 3.6.12.7. The SR is modified by a NOTE that allows the chemical analysis to be performed on either the liquid or resulting ice of each sodium tetraborate solution prepared. If Ice Is obtained from offsite sources, then chemical analysis data must be obtained for the ice supplied.

SR 3.6.12.3 This SR ensures that the alristeam flow channels through the ice bed have not accumulated ice blockage that exceeds 15 percent of the total flow area through the ice bed region. The allowable 15 percent buildup of ice is based on the analysis of the sub-compartment response to a design basis LOCA with partial blockage of the Ice condenser flow channels.

The analysis did not perform detailed flow area modeling, but rather lumped the Ice condenser bays into six sections ranging from 2.75 bays to 6.5 bays. Individual bays are acceptable with greater than 15 percent blockage, as long as 15 percent blockage Is not exceeded for any analysis section.

To provide a 95 percent confidence that flow blockage does not exceed the allowed 15 percent, the visual inspection must be made for at least 54 (33 percent) of the 162 flow channels per Ice condenser bay. The visual inspection of the ice bed flow channels is to Inspect the flow area, by looking down form the top of the ice bed, and where view is achievable up from the bottom of the ice bed. Flow channels to be Inspected are determined by random sample. As the most restrictive ice bed flow passage Is found at a lattice frame elevation, the 15 percent blockage criteria only applies to "flow channels" that comprise the area:

McGuire Units 1 and 2 B 3.6.12-5 Revision No. 47

Ice Bed B 3.6.12 BASES SURVEILLANCE REQUIREMENTS (continued)

a. Between ice baskets, and

b. Past lattice frames and wall panels.

Due to a significantly larger flow area In the regions of the upper deck grating and the lower inlet plenum support structures and turning vanes, it would require a gross buildup of ice on there structures to obtain a degradation in air/steam flow. Therefore, these structures are excluded as part of a flow channel for application of the 15 percent blockage criteria. Plant and industry experience have shown that removal of Ice from the excluded structures during the refueling outage Is sufficient to ensure they remain operable throughout the operating cycle. Thus, removal of any gross Ice buildup on the excluded structures is performed following outage maintenance activities.

Operating experience has demonstrated that the ice bed is the region that is the most flow restrictive, dueto the normal presence of ice accumulation on lattice frames and wall panels. The flow area through the ice basket support platform is not a more restrictive flow area because it is easily accessible from the lower plenum and is maintained clear of ice accumulation. There is not a mechanistically credible method for ice to accumulate on the Ice basket support platform during plant operation.

Plant and industry experience has shown that the vertical flow area through the Ice basket support platform remains clear of ice accumulation that could produce blockage. Normally only a glaze may develop or exist on the ice basket support platform which is not significant to blockage of flow area. Additionally, outage maintenance practices provided measures to clear the ice basket support platform following maintenance activities of any accumulation of ice that could block flow areas.

Activities that have a potential for significant degradation of flow channels should be limited to outage periods. Performance of this SR following completion of these maintenance activities assures the ice bed is in an acceptable condition for the duration of the operating cycle.

Frost buildup or lose ice Is not to be considered as flow channel blockage, whereas attached ice is considered blockage of a flow channel. Frost is the solid form of water that is loosely adherent, and can be brushed off with the open hand.

McGuire Units 1 and 2 B 3.6.12-6 Revision No. 47

Ice Bed B 3.6.12 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.6.12.4 Ice mass determination methodology Is designed to verify the total as-found (pre-maintenance) mass of ice in the ice bed, and the appropriate distribution of that mass, using a random sampling of individual baskets.

The random sample will include at least 30 baskets from each of three defined Radial Zones (at least 90 baskets total). Radial Zone A consists of baskets located in rows 8, and 9 (innermost rows adjacent to the Crane Wall), Radial Zone B consists of baskets located in rows 4, 5, 6, and 7 (middle rows of the ice bed), and Radial Zone C consists of baskets located In rows 1, 2, and 3 (outermost rows adjacent to the Containment Vessel).

The Radial Zones chosen include the row groupings nearest the inside and outside walls of the Ice bed and the middle rows of the ice bed.

These groupings facilitate the statistical sampling plan by creating sub-populations of ice baskets that have similar mean mass and sublimation characteristics.

Methodology for determining sample ice basket mass will be either by direct lifting or by alternative techniques. Any method chosen will include procedural allowances for the accuracy of the method used. The number of sample baskets in any Radial Zone may be increased once by adding 20 or more randomly selected baskets to verify the total mass of that Radial Zone.

In the event the mass of a selected basket In a sample population (initial or expanded) cannot be determined by any available means (e.g., due to surface ice accumulation or obstruction), a randomly selected representative alternate basket may be used to replace the original selection in that sample population. If employed, the representative alternate must meet the following criteria:

a. Alternate selection must be from the same bay-Zone (i.e., same bay, same Radial Zone) as the original selection, and

b. Alternate selection cannot be a repeated selection (original or alternate) in the current Surveillance, and cannot have been used as an analyzed alternate selection in the three most recent Surveillances.

The complete basis for the methodology used in establishing the 95%

confidence level in the total ice bed mass is documented in Ref. 5.

The total ice mass and individual Radial Zone ice mass requirements defined in this Surveillance, and the minimum ice mass per basket requirement defined by SR 3.6.12.5, are the minimum requirements for McGuire Units 1 and 2 B 3.6.12-7 Revision No. 4 7

Ice Bed B 3.6.12 BASES SURVEILLANCE REQUIREMENTS (continued)

OPERABILITY. Additional ice mass beyond the SRs is maintained to address sublimation. This sublimation allowance is generally applied to baskets in each Radial Zone, as appropriate, at the beginning of an operating cycle to ensure sufficient ice is available at the end of the operating cycle for the ice condenser to perform its intended design function.

The Frequency of 18 months was based on ice storage tests, and the typical sublimation allowance maintained in the ice mass over and above the minimum Ice mass assumed in the safety analyses. Operating and maintenance experience has verified that, with the 18 month Frequency, the minimum mass and distribution requirements in the ice bed are maintained.

SR 3.6.12.5 Verifying that each selected sample basket from SR 3.6.12.4 contains at least 600 lbs of ice in the as-found (pre-maintenance) condition ensures that a significant localized degraded mass condition Is avoided.

This SR establishes a per basket limit to ensure any Ice mass degradation is consistent with the initial conditions of the DBA by not significantly affecting the containment pressure response. Ref. 5 provides Insights through sensitivity runs that demonstrate that the containment peak pressure during a DBA is not significantly affected by the ice mass in a large localized region of baskets being degraded below the required safety analysis mean, when the Radial Zone and total ice mass requirements of SR 3.6.12.4 are satisfied. Any basket identified as containing less than 600 lbs of ice requires appropriately entering the TS Required Action for an Inoperable Ice bed due to the potential that It may represent a significant condition adverse to quality.

As documented in Ref. 5, maintenance practices actively manage individual ice basket mass above the required safety analysis mean for each Radial Zone. Specifically, each basket is serviced to keep its ice mass above 725 lbs for Radial Zone A, 1043 lbs for Radial Zone B, and 1043 lbs for Radial Zone C. If a basket sublimates below the safety analysis mean value, this nstance Is identified within the plant's corrective action program, Including evaluating maintenance practices to identify the cause and correct any deficiencies. These maintenance practices provide defense in depth beyond compliance with the ice bed surveillance requirements by limiting the occurrence of individual baskets with ice mass less than the required safety analysis mean.

McGuire Units 1 and 2 B 3.6.12-8 Revision No. 47

Ice Bed B 3.6.12 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.6.12.6 This SR ensures that a representative sampling of accessible portions of ice baskets, which are relatively thin walled, perforated cylinders, have not been degraded by wear, cracks, corrosion, or other damage. The SR is designed around a full-length inspection of a sample of baskets, and is intended to monitor the effect of the ice condenser environment on ice baskets. The groupings defined in the SR (two baskets in each azimuthal third of the ice bed) ensure that the sampling of baskets is reasonably distributed. The Frequency of 40 months for a visual inspection of the structural soundness of the ice baskets is based on engineering judgment and considers such factors as the thickness of the basket walls relative to corrosion rates expected in their service environment and the results of the long term Ice storage testing.

SR 3.6.12.7 Verifying the chemical composition of the stored ice ensures that the stored ice has a boron concentration > 1800 ppm and < 2330 ppm as sodium tetraborate and a high pH, > 9.0 and < 9.5 at 200C, in order to meet the requirement for borated water when the melted Ice is used In the ECCS recirculation mode of operation. Additionally, the minimum boron concentration setpoint is used to assure reactor subcriticality in a post LOCA environment, while the maximum boron concentration is used as a bounding value in the hot leg switchover timing calculation (Ref. 4). This is accomplished by obtaining at least 24 ice samples. Each sample is taken approximately one foot from the top of the Ice of each randomly selected ice basket in each Ice condenser bay. The SR is modified by a NOTE that allows the boron concentration and pH value obtained from averaging the individual samples analysis results to satisfy the requirements of the SR. If either the average boron concentration or average pH value is outside their prescribed limit, then entry into ACTION Condition A is required. Sodium tetraborate has been proven effective in maintaining the boron content for long storage periods, and it also enhances the ability of the solution to remove and retain fission product iodine. The high pH is required to enhance the effectiveness of the ice and the melted ice in removing iodine from the containment atmosphere.

This pH range also minimizes the occurrence of chloride and caustic stress corrosion on mechanical systems and components exposed to ECCS and Containment Spray System fluids in the recirculation mode of operation. The Frequency of 54 months is intended to be consistent with the expected length of three fuel cycles, and was developed considering these facts:

a. Long term ice storage tests have determined that the chemical composition of the stored ice is extremely stable; McGuire Units 1 and 2 8 3.6.12-9 Revision No. 47

Ice Bed B 3.6.12 BASES SURVEILLANCE REQUIREMENTS (continued)

b. There are no normal operating mechanisms that significantly change the boron concentration of the stored ice, and pH remains within a 9.0 - 9.5 range when boron concentrations are above approximately 1200 pm; and

c. Operating experience has demonstrated that meeting the boron concentration and pH requirements has not been a problem REFERENCES 1. UFSAR, Section 6.2.

2. 10 CFR 50, Appendix K.

3. 10 CFR 50.36, Technical Specifications, (c)(2)(ii).

4. UFSAR, Section 6.3.3.10.

5. Topical Report ICUG-001, Application of the Active Ice Mass Management Concept to the Ice Condenser Ice Mass Technical Specification, Revision 2.

McGuire Units 1 and 2 B 3.6.12-1 0 Revisian No.4 7